It is known that batteries that have got into an abnormal state show a large drop in voltage compared to normal batteries and batteries that have deteriorated with age (e.g. capacity degradation and internal resistance degradation). Although degradation occurs over time, battery abnormality (e.g. a minute short circuit) may happen in a short term even to batteries that have been used for a short period of time. In a worst-case scenario, a battery abnormality may cause ignition. Thus, it is important to quickly detect a sign of battery abnormality and detect the battery abnormality.
One presented method for detecting an abnormality in a power storage device involves performing an equalizing process two or more times to equalize a discrepancy in voltage between a plurality of power storage units, determining the existence of a sign of abnormality if a time interval between the equalizing processes is shorter than a specified time length, and detecting a final abnormality on the basis of a charge or discharge capacity or other values detected after determination of the existence of the sign, as is disclosed in PTL 1.